Ductile damage model for metal forming simulations including refined description of void nucleation

TL;DR

This paper introduces a comprehensive ductile damage model for metal forming simulations that incorporates refined void nucleation descriptions, including a new nucleation rule suitable for complex loading conditions, implemented in FEM for practical applications.

Contribution

A novel phenomenological plasticity model with coupled damage and anisotropy, featuring an advanced void nucleation rule and thermodynamic consistency, implemented in Abaqus for metal forming simulations.

Findings

Model accurately predicts damage evolution during large deformations.

New void nucleation rule captures higher nucleation rates under torsion.

Simulation demonstrates robustness and practical applicability of the model.

Abstract

We address the prediction of ductile damage and material anisotropy accumulated during plastic deformation of metals. A new model of phenomenological metal plasticity is proposed which is suitable for applications involving large deformations of workpiece material. The model takes combined nonlinear isotropic/kinematic hardening, strain-driven damage and rate-dependence of the stress response into account. Within this model, the work hardening and the damage evolution are fully coupled. The description of the kinematics is based on the double multiplicative decomposition of the deformation gradient proposed by Lion. An additional multiplicative decomposition is introduced in order to account for the damage-induced volume increase of the material. The model is formulated in a thermodynamically admissible manner. Within a simple example of the proposed framework, the material porosity is adopted as a rough measure of damage. A new simple void nucleation rule is formulated based on the consideration of various nucleation mechanisms. In particular, this rule is suitable for materials which exhibit a higher void nucleation rate under torsion than in case of tension. The material model is implemented into the FEM code Abaqus and a simulation of a deep drawing process is presented. The robustness of the algorithm and the performance of the formulation is demonstrated.